A new study finds that comprehensive background checks aren’t enough to impact homicide numbers. To do that, states also need to adopt licensing laws.

Published in May in the Journal of Urban Health, the study examines which state gun laws actually drive down homicide rates within large, urban U.S. counties, which is where more than 60 percent of firearm homicides happen. Researchers found that gun licensing laws have, by far, the biggest effect. According to the study, more than 14,400 firearm homicides occurred in the U.S. in 2016, accounting for three-quarters of the nation’s homicide rate. Every day, 34 people in America are murdered with a gun.

“We have a growing body of research showing that licensing laws are effective at the state level,” study co-author Cassandra Crifasi, an assistant professor at the Johns Hopkins Center for Gun Policy and Research, told me. “We wanted to see if those protective effects at the state level held true in areas where homicides are concentrated.”

In particular, Crifasi and co-authors examined impacts related to five state gun policies: comprehensive background checks, permit-to-purchase, right to carry, stand your ground and violent misdemeanor prohibitions. Currently, 19 states and Washington, D.C., have comprehensive background check laws, which require all sellers, both private sellers and licensed retailers, conduct background checks on potential gun buyers. Ten states and the District of Columbia have gun-licensing requirements on the books, commonly known as permit-to-purchase laws. These laws typically require that people apply directly with state or local law enforcement for a permit to buy a gun and often give law enforcement up to 30 days or more to complete a thorough background check.

Federal law, on the other hand, requires only licensed gun retailers do background checks — and if the check takes longer than three days, retailers can move forward with a gun sale, though some states have extended that three-day deadline or require a fully completed background check before a sale. (This three-day loophole is how Dylann Roof, who murdered nine people in a church in Charleston, South Carolina, obtained a gun. If the dealer had waited, the eventual background-check results would have prohibited the purchase.)

To tease out which of the five state laws impacted homicide numbers, Crifasi and co-authors used data from the Centers for Disease Control and Prevention’s Wide-ranging Online Data for Epidemiologic Research (WONDER) system, eventually gathering data on 136 counties with populations greater than 200,000 over a 32-year span. They found that state permit-to-purchase laws were associated with a 14 percent reduction in firearm homicides in large, urban counties, whereas states with only comprehensive background check laws were associated with a 16 percent increase in firearm homicide. Right-to-carry laws were associated with a 4 percent increase in firearm homicide; stand-your-ground laws were associated with a 7 percent increase; and violent misdemeanor laws, which prohibit people with such a record from buying a gun, were associated with a 14 percent increase in firearm homicide.

Crifasi and study co-authors Molly Merrill-Francis, Alex McCourt, Jon Vernick, Garen Wintemute and Daniel Webster conclude that: “This study adds to the growing body of evidence that (permit-to-purchase) laws are associated with reductions in firearm homicide. States that are considering a range of policies related to the transfer of firearms should consider a handgun purchaser licensing system through a (permit-to-purchase) law as a mechanism to reduce firearm homicide.”

While the study doesn’t pinpoint exactly why the laws had the effects they did, Crifasi posits that permit-to-purchase laws likely work better because they give law enforcement much longer windows to conduct background checks. In addition, state and local law enforcement often have access to more information and data, increasing the likelihood of screening out people with records that would prohibit gun ownership. Previous research, she noted, has also shown that permit-to-purchase is associated with less diversion of guns into criminal hands.

Surveys show that the great majority of Americans, as well as the majority of gun owners, supports gun licensing laws.

“I think it’s fair to say that local — and even sometimes, state law enforcement — often have a better sense of the dangerous people in their communities,” Crifasi said. “Some licensing laws do allow for discretion, but even with that discretion, the requirement that you have to apply through law enforcement seems to increase accountability.”

In states with only comprehensive background check laws, Crifasi told me she and fellow researchers didn’t expect to see a strong protective effect, but they were expecting to see some protective impact. In fact, in light of the study finding an association between such laws and an increase in homicide, researchers called for further exploration of the connection, noting that “it is possible that comprehensive background check-only laws are harmful.” Crifasi said this particular finding could reflect problems with enforcing such laws or the timeliness and quality of records in the National Instant Criminal Background Check System.

“Comprehensive background checks are a necessary part of the system, but they’re not sufficient on their own and need to be a piece of a more robust system,” she said.

Crifasi said she hopes today’s new movement of young gun control advocates will embrace the research and push for lawmakers to adopt permit-to-purchase laws. She also called on advocates to talk to gun owners in permit-to-purchase states about their experiences obtaining licenses and use those stories to help build public support.

“I hope more young people will start talking about licensing,” she told me. “It’s good for public safety and it’s nothing more than a small inconvenience.”